This invention relates to thermoplastic compositions of interpolymers of .alpha.-olefin monomers with one or more vinylidene aromatic monomers and/or one or more hindered aliphatic or cycloaliphatic vinylidene monomers blended with vinyl halide homopolymers and copolymers.
The generic class of materials of .alpha.-olefin/hindered vinylidene monomer substantially random interpolymers, including materials such as .alpha.-olefin/vinyl aromatic monomer interpolymers, and their preparation, are known in the art, such as described in EP 416 815 A2. These materials, such as ethylene/styrene interpolymers, offer a wide range of material structures and properties which makes them useful for varied applications, such as asphalt modifiers or as compatibilizers for blends of polyethylene and polystyrene, as described in U.S. Pat. No. 5,460,818.
The structure, thermal transitions and mechanical properties of substantially random interpolymers of ethylene and styrene containing up to about 50 mole percent styrene have been described (Y. W. Cheung, M. J. Guest; Proc. Antec '96, pages 1634-1637). These polymers are found to have glass transitions in the range -20.degree. C. to .+-.35.degree. C., and show no measurable crystallinity above about 25 mole percent styrene incorporation, i.e. they are essentially amorphous.
Although of utility in their own right, Industry is constantly seeking to improve the applicability of these interpolymers. To perform well in certain applications, these interpolymers could be desirably improved, for example, in the areas of processing characteristics or enhanced glass transition temperature depression or reduced modulus or reduced hardness or lower viscosity or improved ultimate elongation compared to a like property of the unmodified interpolymer. In relation to this invention, it is also considered advantageous to be able to engineer the glass transition process for materials comprising the interpolymers to a particular temperature range, so that the energy absorbing capabilities of the polymer can be best utilized, for example in sound and vibration damping. U.S. Pat. No. 5,739,200 filed Dec. 17, 1996 describes the improvement in properties of interpolymers of .alpha.-olefin/vinylidene aromatic monomers obtained by adding plasticizers.
Similarly the family of vinyl polymers such as poly (vinyl chloride) (PVC) have found applications in many markets, in part because of their versatility and good balance. This versatility is readily achieved due to the compatibility of the polymer with a range of plasticizers, typically employed at levels which improve flexibility and processability.
The use of polymeric materials to modify the impact properties of rigid PVC is widely known. For example, the addition of polyacrylic resins, butadiene-containing polymers such as acrylonitrile butadiene styrene terpolymers (ABS), and methacrylate butadiene styrene terpolymers (MBS), and chlorinated polyethylene (CPE) resins to rigid PVC is known to increase the impact strength of PVC products such as house siding panels, vinyl window frames, electrical conduit, and blow molded PVC bottles. Impact modifiers are typically used in these applications at from 5 to about 15 parts by weight per 100 parts of PVC resin. The rigid PVC resins typically used in these applications is typically classified as medium or high molecular weight.
In the case of impact modification of low molecular weight or flexible PVC resins, such as are used in injection molding applications, the melt viscosity of the impact modifying material is higher than that of the PVC resin. This fact can result in poor dispersion and broad particle size distribution of the impact modifier with the effect of the low PVC compounds having low impact strength. Some improvement in impact strength can be gained by increasing the amount of impact modifier in the compound but this is often economically counter-productive.
The purpose of this invention is to provide novel blend compositions comprising one or more vinyl halide polymers and at least one substantially random interpolymer of one or more .alpha.-olefin monomers with one or more vinylidene aromatic monomers and/or one or more hindered aliphatic or cycloaliphatic vinylidene monomers. The novel blend compositions, provide materials with improved processing/property attributes over the unmodified polymers comprising the blends. The blend compositions can exhibit a unique balance of properties including enhanced modulus and barrier properties, improved tensile strength, toughness, radio frequency (rf) sealability, solvent bondability, thermal stability, and ignition resistance, depending upon the selection of the individual blend components and their composition ratios.
As a further embodiment, the invention provides novel blend compositions comprising one or more vinyl halide polymers, and at least one substantially random interpolymer of one or more .alpha.-olefin monomers with one or more vinylidene aromatic monomers and/or one or more hindered aliphatic or cycloaliphatic vinylidene monomers in combination with one or more plasticizers. These blend compositions allow for the manufacture of materials for which the location and the breadth of the glass transition can be controlled by varying the blend component composition ratio and plasticizer level. Surprisingly certain blends including a plasticizer show a single glass transition temperature (Tg) from thermal analysis data. In other examples, the blend compositions show multiple Tg's, for example when the level of plasticizer is relatively low. Such blend compositions additionally find utility in applications such as sound management and vibration damping.